jbeal has measurement tables and first impressions in the forum:
I got the eval kit for the TI TMP006 sensor mentioned here last week. It does seem to be able to detect the presence of my hand (apparently about 37 C), when I place it in front of the sensor and then remove it (so the sensor sees just the surface of my desk, around 25 C). The sensor sits in the open on a flat PCB. I wonder if it would be a bit less noisy if it was semi-enclosed and shielded from stray air currents.
Via the comments.